1. Field of the Invention
This invention deals with the treatment of excretory functions including urinary and defecation problems in mammals wherein the normal function is absent or severely impaired.
2. Description of the Art Practices
It is known for most paraplegics that the bladder empties automatically and necessitates the wearing of an external collecting device. Reflex bladder contractions occur where the urethral sphincter may undergo an intermittent spastic contraction interrupting voiding and frequently leading to high bladder pressures. The foregoing situation is also accompanied by incomplete bladder emptying also known as detrusor sphincter-dyssynergia.
Typically, a patient whose sacral cord, or cauda equina is damaged often results in a flaccid bladder. Intermittent self catheterization is often used by patients who are unable to completely void the bladder thus leaving a large residual amount of urine which predisposes the urinary tract to infections.
In addition to patients with spinal injuries, there is also the situation of surgical patients who need to void their bladder. The micturition process in patients under anesthesia may be necessary to prevent abnormally high bladder pressure. Such situation occurs where the patient is in need of urgent surgery, and normal procedures for bladder evacuation must be deferred. Another situation in which micturition may benefit from controlled response is in geriatric patients. In such situations it may be necessary to stimulate the patients bladder in a controlled setting to avoid bed wetting.
Arnold, et al. discusses bladder function in an article entitled Sacral Anterior Root Stimulation of the Bladder in Paraplegics Aust. N.Z.J. Surg. 1986, 56, 119-124. The Arnold article treats the treatment of patients 12 month post-injury to allow the neurological status to become stable. Arnold describes the patient as being positioned in a prone situation and laminectomies of L 3 to S 2 (inclusive) are performed. The dura is then opened in the mid-line at the L 4/L 5 level to S 2 with initial anatomical localization of the cauda equina nerves. Commencing unilaterally, the S 2 nerves are then identified and the motor and sensory components separated. Direct nerve stimulation is performed on the motor and sensory components with observation made of the detrusor and rectal pressures, pelvic floor and distal limb muscles.
The second stage of the operation in Arnold's patient is performed a week later. The patient is positioned in the lateral decubitus position and the coiled cables in the cutaneous pouch are exposed and lead subcutaneously to a radial-receiver unit which is placed in a subcutaneous pouch over the anterial lateral chest wall over ribs.
The transmitter coils are connected by a short cable to the signal generator control box which allows adjustment of the strength and frequency, shape and timing of the desired electro-stimulation. It is observed that voiding occurs in spurts after each burst of stimulation. The procedure of Arnold is difficult to put in practice with only two-thirds of the patients initially indicating a satisfactory response following surgery.
Li, et al, in Role of Electric Stimulation in Bladder Evacuation Following Spinal Cord Transection discusses bladder stimulation in The Journal of Urology vol. 147, 1429-1434. Li teaches neural stimulation as a potentially valuable therapeutic tool in the treatment of neurogenic bladder with detrusor areflexia.
Li discloses that the urinary bladder receives its innervation from 3 sources: Somatic, Sympathetic, and Para-Sympathetic. The Sympathetic innervation of the bladder is controlled by the hypogastric nerve; para-sympathetic impulses are carried by the pelvic nerve. The pudendal nerve which is derived from the sacral nerves supplies somatic innervation to the striated musculature of the urethra. Li notes that the Somatic and Autonomic reflexes are lost in the event of a spinal cord lesion.
A review article was released by Madersvacher entitled Intravesical Electrical Stimulation for the Rehabilitation of the Neuropathic Bladder, Paraplegia 28 (1990) 349-352. Madersvacher stated that introvesical electro-stimulation dates back to 1878 which Saxtroph treated urinary retention by inserting a special catheter trans-uretherally into the bladder with a metal-electrode inside and with a neutral electrode placed supra-pubically. The idea of electro-stimulation of the bladder to encourage functional micturition laid dormant until 1959 when Katona et al described the technique of intraluminal electro-therapy. Madersvacher also discusses trans-urethral electro-stimulation of the bladder being based on the activation of specific receptors in the bladder wall.
Nashold et al, in Electro Micturition, in Paraplegia Arch Surg Vol., February 1972. Nashold describes a paraplegic patients who have undergone electrode implantation in the S 1-S 2 region of the conus mudullaris. The electro-stimulation proceeded with a small battery-operated radio frequency stimulator and the receiver is stated to produce adequate emptying of the bladder every 3 to 4 hours. The male patients were stated to have required a sphincterotomy. Nashold states that the stimulation indexes employed at surgery and during the initial testing were biphasic square wave ranging from 100 to 500 microseconds in duration at various frequencies and voltages. Specific data concerning the parameters of Nashold indicate that the patient at home uses stimulation indexes of 15 to 30 cycles per second, 10 to 15 volts and 200 micro-second pulses for 30 to 60 seconds for emptying the bladder.
Urinary stimulation is discussed in an article entitled Sacral Anterior Root Stimulators for Bladder Control in Paraplegia by Brindley, et al. reported at Paraplegia 30 (1982) 365-381. Brindley discloses that patients whose bladders remain innervated by an isolated cord that is not severely damaged can achieve reflex micturition. However, many of the patients according to Brindley have large residual urine volumes and suffer from a persistently or recurringly infected urine.
Brindley discusses an implant consisting of three parts. The Brindley article discusses the use of electrode "books" in which the sacral roots are trapped with three electrodes in each slot. Brindley discusses avoiding pressure through a thin urethral catheter during implant driven micturition after the implants had been in use for several months.
The discussion of chronically implanted electrodes for treatment of the spinal root is discussed in A Technique for Anodally Blocking Large Nerve Fibres Through Chronically Implanted Electrodes by Brindley, et al Journal of Neurology, Neural Surgery and Psychiatry 1980, 43, 1083-1090 (hereinafter Brindley II).
Mouchawar, in an article entitled Closed-Chest Cardiac Stimulation with a Pulsed Magnetic Field, Medical & Biological Engineering & Computing March 1992, page 162 discusses magnetic stimulator to generate intense, rapidly changing magnetic fields capable of stimulating nerves. Magnetic resonance systems utilizing coplanar coils to provide a pulsed magnetic field with an average of 12 kilojoules to achieve closed-chest magnetically induced ectopic beats. The Mouchawar article also describes the peak-induced electrical field for threshold stimulation at 213 V/m for a 571 micro-second damped sine wave pulse.
Voorhees III et al, in a technical note in the Journal of Clinical Engineering September/October 1990 page 407 article entitled Magnetically Induced Contraction of the Inspiratory Muscles in Dog discusses short-duration inspirations by discharging a capacitor bank into an excitation coil placed over the lower right chest. The Voorhees III article discusses utilizing the construction of the excitation coil as having 59 turns of 1/4 inch copper ribbon 0.0200 inches thick wound on a 3/4" diameter plastic rod where the outer diameter of the coil is 3.75" and the entire coil is potted in silicon rubber.
The inductance per Voorhees III et al is 139 micro-H and the resistance is 0.084 ohms. The current was delivered to the coil from a 100-micro F capacitor bank. The resonant frequency of the system was 1350 Hz and the damping coefficient was 0.05.
Cadwell Laboratories, Inc. in Application Notes AP-2 Rev. 1 Feb. 22, 1990, discusses high speed magnetic stimulator characteristics. In a technical note by Bourland et al in IFMBE, page 106-108 (March, 1990), entitled Transchest Magnetic (eddy-current) stimulation of the dog heart as reported in Med. & Biol. Eng. & Comput., 1990, 28, 196-198. The magnetic stimulator used by Bourland et al is described as a pulse generator with two coplanar coils connected in a series so that the current flows in a clock-wise direction in one coil and counter-clockwise in the other.
The Bourland et al coil and generator specifications were stated to be determined from computer simulations, and were optimized for minimal energy stored in the generator. The coils were described as 30-turn 106 Micro H Coil fabricated from 1/2" by 0.043" copper ribbon covered with a glass-epoxy insulation. The inter-diameter of each coil is 7.2 cm and the outer diameter is 16.5 cm. The magnetic stimulator and coils is a series RLC circuit, comprising a 682 micro F, 9900 V Capacitor, output switch (ignition) and 220 micro H inductor (combined value for both coils, including mutual inductance). The resistance of the Bourland device is stated to be 220 m ohms and a reverse-biased diode is connected across the 682 micro-capacitor to prevent reverse polarization.
A discussion of nerve stimulation was presented in IEE Transactions on Biomedical Engineering, Volume 37, NO. 6, 1990 under the heading of A Model of the Stimulation of a Nerve Fiber by Electromagnetic Induction by Roth et al.
Alexander, et al, in British Journal of Urology (1970), 42, 184-190 discusses electric pessary stimulation in a paper entitled Treatment of Urinary Incontinence by Electric Pessary A Report of 18 Patients.
In an article entitled Developing a More Focal Magnetic Stimulator Part I: Some Basic Principals by Cohen et al, as recorded in Journal of Clinical Neurophysiology, 8 (1); 102-111 (1991) magnetic stimulation is discussed generally. Similar disclosures are made by Yunokuchi et al in the Journal of Clinical Neurophysiology, 8 (1); 112-120 (1991) in an article entitled Developing a More Focal Magnetic Stimulator. Part II: Fabricating Coils and Measuring Induced Current Distributions.
The reader is also referred to Magnetic Stimulation in Clinical Neurophysiology edited by Sudhansu Chokroverty and published by Butterworths, Boston, London, Singapore, Sydney, Toronto, and Wellington Chapter 3 pages 17 through 32, pages showing FIGS. 7-18; 14-1; 17-4; 17-10, 18-3 and 18-4.
Further reference is made to Magnetic Brain Stimulation With a Double Coil: The importance of Coil Orientation by Mills et al. published in Electroencephalography and Clinical Neurophysiology, 85 (1992) pages 17-21. Reference is also made to a publication entitled the Effects of Coil Design on Delivery of Focal Magnetic Stimulation-Technical Considerations Cohen et al. Electroencephalography and Clinical Neurophysiology, 75 (1990) pages 350-357.
Further reading on the subject of magnetic studies of mammals is found in Brodak et al. Magnetic Stimulation of Sacral Roots Neurology and Urodynamics 12: pages 533-540 (1993) and in Motor Evoked Potentials From the Bladder on Magnetic Stimulation of the Cauda Equina: New Techniques for Investigation of Autonomic Bladder Innervation published in the Journal of Urology 147: pages 658-661 (1992).
A summary of the results of the magnetic stimulation presented in this patent was made on Oct. 8, 1993 at the annual meeting of the AAEM Annual Meeting under the heading of High Frequency Magnetic Stimulation of the Inspiratory Muscles. A second presentation to the AAEM Annual Meeting on Oct. 8, 1993 concerned Magnetic Stimulation of the Bladder in Dogs.
To the extent that the foregoing references are relevant to the present invention, they are herein specifically incorporated by reference. Where temperatures are given, they are in degrees C. unless otherwise indicated. Pressure measurements are reported with reference to the reading at pubic symphysis as zero. Percentages and ratios given herein are by weight unless otherwise indicated. Measurements herein are stated in degrees of approximation thereby where appropriate the word "about" may be indicated before any measurement.